A disease of the eye known as macular degeneration has become one of the leading causes of blindness in adults. This disease affects the central retinal area known as the macula which affords acute vision and receives light focused by the cornea and lens. This disease can lead to a gradual or sudden loss of vision to the level of 20/200 or less. Commonly, loss of vision only affects the central retinal area of about 0.25 to 4 square millimeters and does not usually progress beyond this area, thereby leaving 95-99% of the retina unaffected. Thus, reading and driving vision can be lost but peripheral vision remains intact.
Most cases of macular degeneration are untreatable, although laser photocoagulation has been proven to be of some benefit in certain instances. Adding prisms to a patient's glasses, who has this macular degeneration disease, also is ineffective because two things happen. First, the eye moves during normal vision while eyeglasses remain stationary. This causes distortion of the visual image as the eye moves back and forth relative to the surface of a fixed prism in the glasses. This distortion is disabling to clear sight and increases as the power of the prism increases. Secondly, if light is redirected by prismatic glasses, in order to strike the paracentral area of the retina, it must pass outside the nodal point of the eye and therefore create oblique astigmatism. This would create distortion of the image. Thus, such prisms in eyeglasses do not provide a solution to the problem.
An example of eyeglasses having prisms therein is disclosed in U.S. Pat. No. 3,245,745 to Hancock. Examples of typical intraocular lenses are described in the following U.S. Pat. Nos.: 4,010,496 to Neefe; 4,242,760 to Rainin; 4,251,887 to Anis; 4,257,130 to Bayers; 4,277,851 to Choyce; and 4,277,852 to Poler.
Thus, there is a continuing need for providing a viable treatment for macular degeneration.